Boonen, winner of last year's green jersey for the race's points competition, tested positive in an out of competition control by the ministry of the Flemish Community on May 26.
The 2005 world champion and reigning Paris-Roubaix champion was given the support of his Quick Step team at a press conference on Wednesday.
"The integrity of the Tour, and of the teams participating in the Tour, could be harmed."
Christian Prudhomme,
Tour de France director |
However the Belgian, a six-time stage winner at the Tour de France and one of the most well-known faces in cycling, has fallen victim to the race's code of ethics, which has been reinforced in the wake of continuous doping affairs.
A 'good conduct' charter has been signed by all teams participating in the Tour and the race owners, with Prudhomme saying he had already spoken to Boonen and Quick Step team manager Patrick Lefevere to inform him of the decision.
"As far as we are concerned, Tom Boonen is automatically ruled out of the Tour de France as soon as the information concerning his case has been confirmed," Prudhomme said.
Private problems
Lefevere, in supporting his star rider, had earlier stressed the difference between "real doping problems" in cycling and the difficulties of a "private" nature of their star.
Prudhomme recognised the difference in both cases, but said the race could not afford to be associated with riders involved in taking drugs.
"It's not a case of performances being improved, this is something that has happened in a social sphere well outside of sport," added Prudhomme.
"Tom Boonen is a big champion but a big champion must also be exemplary.
"The integrity of the Tour, and of the teams participating in the Tour, could be harmed."
In a statement read at the start of the press conference Boonen apologised for the pain caused to his team and his family.
Not perfect
"I'm not going to defend myself here today but I hurt my family, my friends and my team and I apologise," said Boonen, who has also been barred from competing in the Tour of Switzerland starting on Saturday.
"I've been in the news recently in a negative way. I'm not perfect and I'll accept the consequences. I'm now going to get some rest and I can count on the confidence of my team.
"I hope that the fans will continue to support me. They will soon be able to count on my unreserved commitment."
The Flemish Community, in charge of doping controls in the north of the country, said they will not be taking any action against Boonen, nor will he face sanctons from the International Cycling Union (UCI).
"If the information is confirmed as it is an out-of-competition control, UCI rules like those of the World Anti-Doping Agency (WADA) do not provide for any sanctions for cocaine," a UCI spokesman said on Tuesday.